In general, magnesium alloy materials have the lowest density among alloys in practical use, lightweight and high strength and accordingly have been promoted for applications to casings of electric products, wheels of automobiles, underbody parts, peripheral parts for engines, and the like.
In particular, with respect to parts for uses relevant to automobiles, since high mechanical characteristics are required, as magnesium alloy materials containing an element such as Gd, Zn and the like, materials with specified configurations have been manufactured by a single-side rolling method and a rapid solidification method (e.g. Patent Document 1, Patent Document 2, and Non-Patent Document 1).
However, in specified manufacturing methods, although providing the above-mentioned magnesium alloy materials with high mechanical characteristics, there are problems that special facilities are required, the productivity is low, and further applicable parts are limited.
Therefore, conventionally, there have been proposed methods for manufacturing magnesium alloy materials in which even plastic processing (extrusion) is conducted from common melt casting with high productivity without using special facilities or processes described in the above-mentioned Patent Documents, mechanical characteristics useful for practical applications can be obtained (e.g. Patent Document 3 and Patent Document 4). The magnesium alloy materials disclosed in Patent Documents 3 and 4 are known to have high mechanical characteristics.    Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 06-041701    Patent Document 2: JP-A No. 2002-256370    Patent Document 3: International Publication No. 2005/052204 Pamphlet    Patent Document 4: International Publication No. 2005/052203 Pamphlet    Non-Patent Document 1: Lecture Summary, the 108th Conference of Japan Institute of Light Metals, P 42-45 (2005)